This invention relates to a fluid jet loom such as an air jet loom and more particularly to a device for inserting the weft yarns into the weft guide channel of the loom by the selective use of a plurality of weft-inserting main nozzles.
In actuating a plurality of main nozzles in accordance with a weft yarn selection program for selectively inserting plural weft yarns supplied from plural weft yarn supply sources into warp sheds, it is known to direct the axes of the jets from the several fixed weft-inserting main nozzles parallel to the weft yarn guide channel. In the case of what is called the modified reed, in which recessed guide apertures are formed on the front sides of the reed teeth for forming a weft yarn guide channel in the reed itself, the forward end of the weft yarn, as it is projected from the main nozzle along the jet axis of the main nozzle in the vicinity of these yarn exit apertures of the reed teeth, is apt to escape through the open side of the reed at the outset of weft insertion.
The Japanese Laid-open Utility Model Publication No. 19075/1978 shows an example of a weft-inserting device designed to eliminate the above described drawback caused by forming the weft guide channel with a larger opening area in the modified reed. The prior-art device makes use of a pair of weft-inserting main nozzles. One of these main nozzles has its jet axis directed towards the recessed wall surface opposite to the opening side of the channel whereas the other main nozzle has its jet axis directing to the opening side of the channel. A set of auxiliary nozzles are provided on the opening side, facing and in the direction of the jet axis of the other main nozzle.
With the above described prior-art device, it is necessary to provide these auxiliary nozzles in order to prevent the forward ends of the weft yarns, as they are projected along the jet axis towards the opening side of the weft yarn guide channel, from exiting through the opening side of the channel. Thus, these auxiliary nozzles have a function which is different from that of conventional auxiliary nozzles, which is to assist in the forward travel of the weft yarns. This results in an increased number of component parts with increased costs and a complicated design.
In a jet loom adapted to project the weft yarns from the weft yarn main nozzle into the warp shed, there is also known a weft-inserting system wherein a large number of weft yarn guide members are juxtaposed in the weft-inserting direction for defining the yarn guide channel and wherein a set of auxiliary nozzles is arranged between the reed and the weft yarn guide members to assist in the forward travel of the yarn projected and inserted in the guide channel. This system makes it possible to reduce the jet pressure, while also preventing the risk of yarn breakage and reducing the consumption of the jet fluid. The effect may be further improved by having a smaller cross-sectional area of the weft yarn guide channel.
However, in the weft-inserting system shown in the Japanese Publication No. 19075/1978, since the weft yarn guide channel is naturally provided with an opening to permit the weft yarn to escape therethrough prior to beating the yarn to the previously inserted yarn, the forward end of the weft yarn projected from the main nozzle whose jet axis is directed, towards the opening side is apt to exit therethrough, thus causing a failure in weft insertion and thereby affecting operating efficiency.
Thus, the main nozzle disposition shown in the Japanese Publication No. 19075/1978 can be used only with a sacrifice in the operating efficiency of the loom.
On the other hand, when the plural weft-inserting main nozzles are not fixed, it is necessary to provide means whereby the respective weft-inserting main nozzles may be selectively positionally switched to the weft-inserting position aligned with the weft yarn guide channel. As an example of such switching means, the Japanese Laid-open Patent Publication No. 133248/1982 shows a cam mechanism driven in time with the rotation of the loom to cause rocking of an associated shaft in such a manner that a pair of weft-inserting main nozzles on a bracket secured to the shaft may be positionally switched to the weft-inserting position.
However, in the cam-actuated weft-inserting system, each weft insertion pattern is associated with a specified cam profile so that cam replacement is necessary whenever a new weft insertion pattern is selected. In addition, the cam profile is necessarily complicated even when the pattern is complicated only slightly. This means that the weft insertion pattern is rather simple, despite the fact that the troublesome operation of replacing the cam needs to be performed when changing the weft insertion pattern. Also, problems are sometimes presented in that the positional switching of the main nozzles is unable to keep up with the operation of the high speed loom.
The Japanese Laid-open Patent Publication No. 43148/1984 shows an example of the weft-inserting device wherein the weft insertion pattern can be changed freely without changing the cams. Thus, a pair of magnetic solenoids may be energized or deenergized for driving two pins to thereby switch the pair of main nozzles supported by a lever to permit the desired setting of the weft yarn selection program or the weft insertion pattern. However, in the prior-art device, a large number of rotary levers are required for converting the rotary movement of the cam into the main nozzle switching operation. Moreover, the main nozzle is difficult to affix to the sley so that the lever supporting the pair of main nozzles needs to be swung in time with the sley, resulting in a complicated device. The driving pins and the lever need to be engaged with high accuracy, but such is possible only with considerable difficulties. Problems are also presented in regarding compatibility of the arrangement with the operation of a high speed loom such as a jet loom. In addition, with an increase in the number of the main nozzles, the structure and cam profile also become increasingly complicated so that it becomes extremely difficult to selectively introduce three or more weft yarns.
The Japanese Laid-Open Patent Publication No. 142747/1980 shows an example of the device for selective insertion of four weft yarns with the use of four main nozzles. In the prior-art device, two main nozzles are placed on top of two horizontally arranged main nozzles, these nozzles being vertically and transversely movable for selectively placing one of these nozzles in the weft-inserting position. However, in the device of the Japanese Publication No. 142747/1980, two driving units are required for shifting the main nozzle vertically and transversely thus resulting in increased complicity in the structure and driving control, and difficulty in achieving fast response for cooperation with the high speed loom.